"The treaty itself has been a very efficient tool to improve the U.S.-Mexico relationship," Mexico's economy minister, Ildefonso Guajardo told Bloomberg on Feb. 27.

But Trump and many of his supporters hold the opposite view. They blame NAFTA, which became law in 1994, for a flood of U.S. manufacturing jobs moving to Mexico.

Congressional nonpartisan research concluded in 2015 that NAFTA did not trigger an exodus of jobs. According to the U.S. Chamber of Commerce, 14 million U.S. jobs depend on trade with Mexico and Canada.

Still, Trump and many manufacturing workers cite NAFTA as the top reason for many lost jobs.

However, Trump made clear in February during Trudeau's visit to Washington that he doesn't have a problem with the U.S.-Canada trade relationship. Trump's issue with NAFTA is entirely with Mexico.

"We have a very outstanding trade relationship with Canada," Trump said on February 13, adding that he only plans on "tweaking" NAFTA in parts that affect the U.S. and Canada.

Now Trump wants a new agreement and threatens to withdraw the U.S. from NAFTA if he doesn't get a better deal. He's also threatened to use tariffs against Mexican goods as a negotiating tactic.

His commerce secretary, Wilbur Ross, said last week negotiations for a new trade deal should begin in the latter part of this year. All three sides are willing to update the agreement, but Trump's team has been thin on details about what exactly a better deal looks like.